574 



SCIENCE-GOSSIP. 



ARMATURE OF HELICOID LANDSHELLS AND NEW 

 FORMS OF PLECTOPYLIS. 



By G. K. Gude, F.Z.S. 



{Continued from page 246.) 



pLECTOPYLIS smithiana (i) (figs. 38^-^). I also 

 found two specimens in the Theobald collection 

 of the British Museum, labelled Pleciopylis hrachy- 

 pkcta, which, in spite of some external resemblance 

 to that species, presented sufficient differences to 

 lead one to suspect that they were distinct, and on 

 opening one of them I found that the difference in 

 the armature confirmed this suspicion. In basing 

 a new species upon them, I have much pleasure in 

 dedicating it to Mr. Smith, whose permission to 

 open the shell enabled me to investigate the 

 matter. 



Plectopylis smithiana differs from P. brachypUda in 

 being darker and larger. The ribs are coarser and 



Fig. 38. — Plectopylis smithiana. 



the whorls more convex ; the last whorl is not 

 angulated above, and it widens more towards the 

 aperture. The peristome is less thickened and 

 more reflexed, and the ridge of the parietal callus 

 less stout but more raised, while the umbilicus is 

 wider and much more shallow. The horizontal 



0) Plectopylis smithiana, n. sp. (figs. 38a-rf).— Shell dextral, 

 discoid, widely umbilicated, rufous brown, coarsely and 

 regularly ribbed, with scarcely visible microscopic sculpture 

 above, but strongly decussated with spiral lines below, 

 suture impressed. Whorls 6, convex, slowly increasing, the 

 last rapidly widening towards the aperture, not angulated 

 above, shortly descending in front. Aperture sub-triangular ; 

 peristome light brown, a little thickened and reflexed, the 

 margins converging; parietal callus with a strongly raised 

 flexuous ridge, separated from both margins of the peris- 

 tome. Umbilicus very wide but shallow. Parietal wall, 

 with an entering flexuous horizontal fold, united to the ridge 

 at the aperture, and at one-third of the circumference from 

 the aperture with one crescent-shaped vertical plate, which 

 has two small denticles, one above and one below, on the 

 anterior side. Palatal folds 6, the first and sixth thin and 

 horizontal, the other four short, broad and oblique.— Major 

 diameter, 27 millimetres ; minor diameter, 21 millimetres ; 

 axis, 10 millimetres. — Habitat, Attaram, Burma.— Type in 

 the British Museum. 



parietal fold deflects more at the aperture and 

 there is only one vertical plate (see fig. 38^), which 

 is crescent-shaped, with the convex side towards 

 the aperture ; on its anterior side, in place of a 

 second vertical plate as in P. brachyplecta, are 

 found two elongated, oblique, converging denticles, 

 one above and one below. The palatal armature 

 is similar to that of P. brachyplecta. Fig. 38^, which 

 shows the parietal wall, is from one of the specimens 

 in the British Museum. Figs. ^Sa-c are drawn 

 from a specimen, labelled Attaram, obligingly 

 lent to me by Miss Linter, of Arragon Close, 

 Twickenham, who informs me that she received 

 it from Mr. Theobald. This was also labelled 

 P. brachyplecta, but I have no hesitation in referring 

 it to the new species. It measures — major diameter, 

 26 millimetres ; minor diameter, 21 millimetres ; 

 axis, 9 millimetres. 



Plectopylis plectostoma (figs. 39fl-c) was first de- 

 scribed by Mr. Benson in the " Journal of the 

 Asiatic Society of Bengal," v. (1836), p. 351; but 

 from additional material received, which enabled 

 him to examine the armature, he subsequently 

 published an amended description ("Annals and 

 Magazine of Natural History " (3), v. (i860), 

 p. 247). The species appears to be of fairly 

 wide distribution, for, in addition to the original 

 locality, Darjeeling, Mr. G. Nevill (Handlist (1878), 

 p. 71) records the following habitats: Burma — 

 Bassein and Arakan ; Assam — Sylhet, Khasia 

 and Naga Hills; while Lieut. -Colonel Godwin- 

 Austen mentions specimens from the Dafla Hills, 

 in Assam. The shell has been figured in Reeve's 

 " Conchologia Iconica," t. 129, f. 782 (1852), in 

 Martini und Chemnitz's " Conchylien Cabinet," 

 2nd ed. i., t. 64, ff. 19-21 (1853), and in Hanley and 

 Theobald's "Conchologia Indica," t. 13, f . 2 (1870). 

 The armature was figured by Lieut. -Colonel Godwin- 

 Austen in the "Proceedings of the Zoological 



<==»^ 



-=>'=^ 

 -S^ 



Fig. zg.— Plectopylis plectostoma. 



Society," 1874, t. 73, f. 2. After looking over a 

 number of shells in various collections, I found that 

 two different forms, one with and one without a 

 horizontal fold given off from the parietal vertical 



